Measurement system for quartz crystal microbalance sensors

Human olfactory is studied for a long time and in many ways, and many of them are based on gas chromatography technology. They have used gas sensors made of metal-oxide semiconductors. The semiconductor sensors can detect gases as difference in electric resistance by oxidation or reduction of surface on the sensor. Human olfactory is organized by about 2,000 receptors of smell, and many electric sensors are used to emulate the receptors. We consider applying multi-channel QCM for these sensors. However, QCM sensors in a chamber (small box) interfere with each other, and we should examine measures of a design method for anti-interference. In this paper, we propose a design method and build an evaluation system.     

An operator-splitting method for a liquid crystal model

In this paper an operator-splitting method is applied to find the micro-structure of a liquid crystal model with a simplified Oseen-Frank energy functional. Both projection and penalty methods are used to deal with the constant length constraint. The methods are implemented to compute director fields of liquid crystal slabs of various shapes and with various boundary data. The computational results verify researcher expectations. Some new singularity patterns are observed as well.     

Single crystal silicon nano-wire piezoresistors for mechanical sensors

A p-type silicon (Si) nano-wire piezoresistor, whose minimum cross-sectional area is 53 nm/spl times/53 nm, was fabricated by combination of thermal diffusion, EB (electron beam) direct writing and RIE (reactive ion etching). The maximum value of longitudinal piezoresistance coefficient /spl pi//sub l[011]/ of the Si nano-wire piezoresistor was found to be 48/spl times/10/sup -5/ (1/MPa) at surface impurity concentration of 5/spl times/10/sup 19/ (cm/sup -3/) and it has enough sensitivity for mechanical sensor applications. The longitudinal piezoresistance coefficient /spl pi//sub l[011]/ of the Si nano-wire piezoresistor increased up to 60% with a decrease in the cross sectional area, while transverse piezoresistance coefficient /spl pi//sub t[011]/ decreased with a increase in the aspect ratio of the cross section. These phenomena were briefly investigated based on a hole energy consideration and FEM (finite element method) stress analysis.     

Optimal performance of CMOS compatible IR thermoelectric sensors

This paper presents a theoretical and empirical study of the optimal performance of CMOS compatible infrared thermoelectric sensors with varying pixel area and different aspect ratio of the pixels for two possible sensor structures: cantilever and bridge types. Optimal performance is analyzed analytically, using simplifying assumptions. This analysis is verified by comparing with the exact simulations as well as by comparing with measured results. The resistance of optimized sensors in the sense of minimal noise equivalent power (NEP) is shown to be independent of aspect ratio, but proportional to the third root of the pixel area. The product of the optimal NEP and the square root of the time constant is shown to be constant with varying aspect ratios, while the same applies with the time constant to the power of 3/8 for varying areas. The measured sensors exhibit NEP's down to 13.5 nW in a 300-Hz bandwidth and time constants up to 30 ms     

铌酸锂晶片热释电红外探测器设计及性能测试

通过红外热释电探测器工作原理的分析,采用合适的半导体加工工艺将铌酸锂晶体母材减薄,并对减薄后铌酸锂晶片进行溅射、镀膜将其制成红外敏感单元。选用CMOS放大器与匹配的电阻、电容组成前置放大电路,对热释电信号进行放大和转换;根据红外光谱吸收原理,在敏感单元前封装了窄带滤光片从而提高了敏感单元选择吸收的性能。将敏感单元、前置放大电路和窄带滤波片三部分封装在一个壳体内,红外探测器制作成功。设计了信号调理电路,对从探测器得到的热释电信号进行二次放大和滤波;搭建了探测器响应测试系统,对探测器的性能进行测试,测试验证了该探测器设计的合理性。     

Observations of typhoon eye using SAR and IR sensors

In this review, recent studies on the observations of typhoon eyes by images acquired by multiple sensors, including synthetic aperture radar (SAR), and infrared (IR) radiometer, are first summarized. Large horizontal distances between typhoon eyes on the ocean surface by SAR and those on the cloud top by IR sensors have been demonstrated; these have previously been ignored but should not be ignored in typhoon forecasts and numerical simulations. Then, based on nine published typhoon cases, the horizontal shifts and vertical tilt angles from the cloud-top typhoon eye locations by IR sensors on board the Feng-Yun 2 (FY-2) and Multi Functional Transport Satellite (MTSAT) to those at sea surface by SAR are further estimated. This shift difference between different sensors raises an issue on project distortion and navigation system errors for FY-2 and MTSAT satellites, which are of concern to both space agencies and data users. Finally, issues for current ongoing study and future research related to typhoon eyes are discussed, including rainband tracking between sensors for local wind speeds.     

Anisotropic fluorophors for liquid crystal displays

Liquid crystal displays (LCDs) are commonly found in portable equipment. The main criticisms aimed at these displays are their asymmetric angle-of-view and dull grey appearance, which is particularly acute in low ambient lighting. However, by the inclusion of a fluorescent dye, it is possible to fabricate partially-emissive LCDs with a virtually hemispherical angle-of-view. This effect has been demonstrated succesfully for a range of dyes based on the perylene diester chromophor. An energy transfer mechanism between the liquid crystal host and dye molecule has been identified. This effect was used to enhance the fluorescence intensity.     

多眼红外传感器检测目标温度分布技术研究

大量的工业生产测试设备及家用电器需要对目标温度进行多点精确测量,尤其是温度分布情况.本文研究使用多眼单列红外传感器对目标表面温度分布测量的方法.它使用步进电机控制传感器视场对目标温度扫描,采集环境温度对目标温度值进行补偿,数据通过放大及模数转换后经|<'2>C接口送人主机进行算法补偿,并及作为处理器进行判断的依据.实践...     

Optimization and comparison of photonic crystal resonators for silicon microcantilever sensors

Microcantilever sensors have been known as a fundamental design used in force sensors, strain sensors and biochemical sensors. The fast-growing applications in nanoelectromechanical systems (NEMS) lead to strong demands in new sensing mechanism in order to downsize the sensing elements to nanometer scale. Photonic crystal (PC) based resonators have been investigated as promising solutions because the bandgap structure and resonator characteristics are extremely sensitive to the deformation and position shift of holes in PC resonators. In addition to the well-known nano-cavity resonator (NCR), we proposed hexagonal nano-ring resonators (NRR) of two different layout configurations. When a microcantilever under different force loads, both of the resonant wavelength and the resonant wavelength shift can be measured as a linear function of force load. The linear relationship between wavelength shifts and strain is observed as well. The minimum detectable force and detectable strain for NRR configuration 1 is derived as small as 0.0757 μN and 0.0023%. The outstanding sensing capability renders PC resonators as a promising nanomechanical sensing element to be integrated in various transducers for NEMS applications.     

Progress toward a liquid crystal contact lens display

A contact lens embeddable display using electro‐optic modulation was designed and fabricated. Using a guest–host liquid crystal configuration, a spherically deformed liquid crystal cell was fabricated comprising poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT : PSS) as a conductive layer and obliquely evaporated SiO₂ as an alignment layer. An additional SiO₂ buffer layer was evaporated on top of the PEDOT : PSS to overcome compatibility problems with the patterning of the photolithographically defined spacers. Although the contrast is modest, a patterned modulation could clearly be observed, indicating that our approach and fabrication process could eventually lead to a fully pixelated contact lens display.     

Mixed-mode twisted-nematic cell for transmissive liquid crystal display

Computer simulation results on various mixed-mode twisted-nematic (MTN) cells for transmissive liquid crystal displays are presented. Twist angles ranging from 30 to 120° were investigated. These transmissive MTN cells are attractive for their low operation voltage and fast response time.     

Effect of small liquid crystal molecules on the driving voltage of cholesteric liquid crystal displays

In order to achieve a lower driving voltage of a cholesteric liquid crystal display (Ch-LCD) we formulated new nematic liquid crystal mixtures with dopants. The interesting thing is that the driving voltage is decreased more by adding the low molecular weight of liquid crystal materials in the cholesteric mixtures without decreasing its reflectivity. The cholesteric mixture is optimized by adding 20 wt% of CN-007 enough to drive the display, necessary for using a commercial STN driver. Homogeneous alignment layers provide a higher reflective panel because of stabilizing the planar texture of cholesteric liquid crystal, while homeotropic alignment layers provide a higher contrast ratio because of stabilizing focal-conic structure. The rubbing condition depending on the driving scheme also affects the panel properties. The combination of the panel structure and the process condition of cholesteric mixtures make the Ch-LCD high reflectivity and contrast ratio. Two 5.7 in. VGA monochromic cholesteric reflective liquid crystal displays with a high resolution like this folding type are demonstrated using a STN driver.     

Microstereophotolithography using a liquid crystal display as dynamic mask-generator

 A new laser microstereophotolithography process has been developed in our laboratory to manufacture three-dimensional parts with a high accuracy. As usual in laser stereophotolithography or laser microstereophotolithography, the part is manufactured layer by layer by a light-induced space-resolved polymerization. Until now, in all the already existing microstereophotolithography devices a layer is manufactured vector by vector, by moving the part beneath the initiating light source which remains motionless. We developed a simpler and easier process, in which we can manufacture an entire layer by irradiating its whole surface only once: we used a liquid crystal display as a dynamic generator of masks. In the device we set up, we need only one mobile element, the z translator, all the others are fixed. We manufactured several different 3D microparts, in particular a piece of bevel microgearing with helicoidal cogs, the volume of which is less than half a cubic millimetre. Received: 14 December 1995 / Accepted: 16 September 1996     

Analysis of IR thin-film transmission spectra of liquid tri-n-propylamine

A detailed numerical analysis of infrared thin-film transmission spectra of liquid tri-n-propylamine, measured in layers ranging from 1.8 to 21.6 μm, was carried out. The spectrum of the absorption index, k(υ), was determined and the number of bands was estimated with the use of differentiation and Fourier self-deconvolution. Subsequently optimization of band envelopes and calculation of band intensities was carried out.Vibrational frequencies and potential energy distribution were calculated and tentative band assignements were proposed for numerous observed bands. A considerable coupling of modes was demonstrated.     

Electro-optical properties of a twisted hybrid aligned nematic mode for reflective liquid crystal displays

Abstract— A twisted hybrid aligned (THA) mode is proposed for reflective liquid-crystal displays. In the reflective configuration, a single polarizer and a reflective electrode are used to achieve electrooptical switching between the black and white states in the THA mode of a chiral nematic liquid crystal. Numerical simulations are performed to optimize the cell parameters such as the cell thickness and the amount of the twist in the hybrid geometry. The reflective THA mode is found to give wider viewing and faster response characteristics than a twisted nematic one. The role of an optical retardation film on device performance of such a reflective THA cell is also discussed.     

液晶显示多级汉字菜单的方法

:以 8 0 31单片机控制MGLS - 2 4 0 12 8液晶显示器为例 ,介绍利用CCDOS中的汉字库(HZK16 )实现多级汉字菜单显示的方法。当显示内容改变时 ,只需更改菜单参数 ,而不需更改程序 ,即可显示。     

Functionalization of microfluidic devices for investigation of liquid crystal flows

Systematic studies of thermotropic liquid crystals in confinement, such as liquid crystals in microfluidic channels, require control of the anchoring conditions on the surfaces. Especially for the case of uniform planar anchoring, the standard method involves a mechanical treatment (rubbing) of the surface that is not applicable to microfluidic devices. In the present study, we report methods for the achievement of well-defined anchoring conditions for liquid crystals in microfluidic channels consisting of polydimethylsiloxane and glass. Various physico-chemical techniques enable to establish homeotropic, degenerate planar, uniform planar, and hybrid anchoring conditions on the surface of the channel walls. We characterize the treated surfaces in terms of wettability and liquid crystal anchoring and determine the director field in the microchannels for the different anchoring configurations using polarizing optical microscopy and fluorescence confocal polarization microscopy. The relevance of the surface anchoring for the flow behavior of the liquid crystal in the microchannel is demonstrated by studying the onset of defect-mediated chaotic-like flow at high Ericksen numbers for the different anchoring cases.     

一种斩波失调稳定仪表放大器的研究与设计

采用斩波失调稳定技术设计了一种包括辅助运放和主放大器的仪表放大器.辅助运放采用内置解调器结构,形成低噪声和低失调电压来调节主运放的噪声和失调,使输出极点成为主极点,无需低通滤波器.仪表放大器的带宽由主运放决定.本电路采用TSMC 0.35μm 5 V混合信号工艺设计,利用Cadence公司Spectre进行仿真.结果表明,电路开环增益达87.3 dB,增益带宽积12MHz,共模抑制比可达117 dB.     

Optical bounce in a multi-domain vertical aligned liquid crystal display

Optical bounce phenomenon often occurs in a multi-domain vertical aligned (MVA) mode liquid crystal display (LCD). It results in the double image edge and motion image blur of the LCD. We find that the optical bounce phenomenon is due to nowadays overdriving method. Some suitable change of the method may eliminate the optical bounce phenomenon.